fix hmac algorithm lookup for names without a hashlib attribute

src/hookrelay/signature.py

@@ -5,10 +5,12 @@
 
 
 def compute(secret: str, body: bytes, algorithm: str = "sha256") -> str:
-    algo = getattr(hashlib, algorithm, None)
-    if algo is None or algorithm not in hashlib.algorithms_available:
+    if algorithm not in hashlib.algorithms_available:
         raise ValueError(f"unsupported algorithm: {algorithm}")
-    return hmac.new(secret.encode("utf-8"), body, algo).hexdigest()
+    # pass the name straight to hmac/hashlib.new instead of getattr(hashlib, ...):
+    # some entries in algorithms_available (ripemd160, sm3, sha512_224, md5-sha1)
+    # have no matching hashlib module attribute and would falsely raise here.
+    return hmac.new(secret.encode("utf-8"), body, algorithm).hexdigest()
 
 
 def verify(

tests/test_signature.py

@@ -45,3 +45,13 @@ def test_verify_empty_provided():
 def test_unsupported_algorithm():
     with pytest.raises(ValueError):
         compute("secret", b"x", algorithm="rot13")
+
+
+def test_compute_algorithm_without_hashlib_attribute():
+    # ripemd160 is in hashlib.algorithms_available on most builds but has no
+    # hashlib.ripemd160 attribute, so getattr(hashlib, ...) would wrongly
+    # reject it even though it's a valid, config-approved algorithm.
+    if "ripemd160" not in hashlib.algorithms_available:
+        pytest.skip("ripemd160 not available on this build")
+    expected = hmac.new(b"secret", b"x", "ripemd160").hexdigest()
+    assert compute("secret", b"x", algorithm="ripemd160") == expected